1. Technical Field
This disclosure relates to circuits that automatically select and deliver the highest of multiple different input voltages to an output.
2. Description of Related Art
Some analog systems may need to automatically deliver the maximum of two or more input voltages. A maximum voltage selection circuit may be used for this purpose.
Such a circuit may need to operate continuously. This could impose a continuous load burden, which could be a problem for applications that rely on a battery for operation. A maximum voltage selection circuit that does not draw any quiescent current from any of its inputs or from its output may be highly desirable in such applications.
Efforts to address these needs have been made. See, e.g., U.S. Pat. No. 5,304,864, entitled “Analog Maximum/Minimum Selector Circuit,” U.S. Pre-Grant Patent Publication US2014/0232435A1, entitled “Analog Minimum or Maximum Voltage Selector Circuit,” and Y. Zhang et al., “Input-Self-Biased Transient-Enhanced Maximum Voltage Tracker for Low-Voltage Energy-Harvesting Applications”, IEEE Trans. On Power Electronics, Vol. 27, No. 5, pp. 2227-30 (May 2012). However, these techniques may require bias current in amplifiers to generate the maximum voltages. In addition, these techniques may require complex and costly circuitry. These approaches may also limit the input voltages, such as to a maximum of 5 volts.